Torque converters used in the automatic transmissions of motor vehicles include vaned elements that form a substantially toroidal flow passage for the kinetic fluid in the torque converter. The stator, also known as reactor, the impeller or pump, and the turbine are each formed by an outer housing forming an outer wall of the toroidal path, a shroud forming the inner wall of the toroidal path, and a series of vanes between the housing and the shroud for controlling the flow of fluid through the toroidal path.
The impeller and the turbine are similarly shaped in a semi-toroidal shape as one is the driving member coupled to the input member driven by the engine, and the turbine is the driven member coupled to the output member leading into the transmission. It was previously known to assemble the vaned elements by including tabs on the vanes which entered apertures in the shroud and the housing. The tabs could then be coldworked to retain the vanes in a fixed position with respect to the shroud and the housing. An improved method of assembling vaned elements, which may be used in conjunction with the present invention, is disclosed in U.S. Pat. No. 4,868,365, and in which the tabs are laser welded in recesses of the outer housing.
While it is typical to align tabs with recesses in the housing and in the shroud, such alignments can be difficult to accomplish in automated production. For example, it is preferable to employ a flat blades in constructing the vaned elements, but vanes having a simple cross-sectional shape can be easily deformed. As a result, it has been extremely difficult to automate the installation of such vanes. Registration of the tabs with the recesses, particularly within the small tolerances which permit insertion into the openings, can be extremely difficult when the vanes are easily deformed from their intended shape. Thickening of the blades in order to retain the shape would be undesirable since it substantially increases the mass of material. Since a turbine must be moved by the kinetic fluid, such a construction substantially reduces the efficiency of the torque converter, and adds to the weight and material cost of the vehicle.
One previously known vane improvement avoiding this problem was a rib stamped within the body of the vane in order to maintain the dimensional stability of the vanes as they are transported, stored and delivered to an assembly operation. Unfortunately, it has been found that such ribs substantially increase the turbulence in the kinetic fluid flow through the torque converter. Such turbulence has a substantial impact on the energy transfer efficiency of the torque converter, particularly at the higher engine speeds which are becoming conventional in the industry in order to improve the efficiency of operating motor vehicles.
Other previously known improvements in blade design and fluid couplings address the strength or ease of assembly of the turbine components, and do not address the efficiency problem. For example, U.S. Pat. No. 3,891,350 discloses a torque converter impeller with a rib formed by a flange which seats on the inner surface of the housing for increased durability and rigidity of the blade structure. However, such a rib increases the difficulty of assembling the rib to the outer shell in proper alignment and thus may interfere with efficient fluid flow through the torque converter. Furthermore, the rib substantially adds to the weight of the impeller. U.S. Pat. No. 2,799,228 to Farrell discloses a vane construction in which paper vanes are coated by electrolytically plating with metal, and installed between members constructed in the same manner. Such a construction substantially complicates an automated assembly operation while reducing the mass of the vaned elements.
U.S. Pat. No. 4,098,080 to Pogorelov et al. discloses a conventional tongue attachment for vanes which is implemented by a plate extending through openings in the vane, and the vane is hydrodynamically profiled with varying cross-sectional shaping. U.S. Pat. No. 3,981,614 to Helmer discloses a blade construction in which a liner shell corresponding to the housing shape and the blades are cast together. The liner shell is secured to the adjacent housing for the impeller. These constructions substantially add to the mass of the vaned elements.
Substantially different techniques are also known for use in improving the efficiency of torque converters. For example, U.S. Pat. Nos. 4,944,374 to Casse et al., 4,926,988 to Kundermann and 4,697,417 to Billet et al. disclose improved torque converters which employ a clutch between the turbine and the torque converter casing to provide a lockup under certain conditions. However, the addition of a clutch between the element and the casing provides substantially more complex controls and parts than is required with vane improvements.